I found an interesting whitepaper „Securing the Enterprise with Intel AES-NI“ from Intel.
This white paper explains how the new AES-NI instructions in Intel Xeon 5600 series can improve the AES encryption/decryption. When I read the first time about this feature I was impressed.
OpenSSL (AES part) is up to 7 times faster with this new instruction set.
Intel did also some tests with Oracle 11g and Transparent Data Encryption (TDE) in AES-256 CBC mode. The usage of the optimized Intel Integrated Performance Primitives (IPP) shows an 89 percent reduction (3.33 GHz Xeon X5680 vs 2.8 Intel Xeon X5560) against a previous processor.
This is a huge advantage and if you use TDE you should think about using such a new processor.